Sepsis is the presence in the blood or other tissues of pathogenic microorganisms or their toxins combined with the host's inflammatory response, known as systemic inflammatory response syndrome (“SIRS”) caused by the infection. The immune response is mediated by a class of proteins called toll-like receptors (“TLR”) that recognize structurally-conserved molecules broadly shared by microorganisms but which are distinguishable from host molecules.
Once microorganisms have breached barriers such as the skin or intestinal tract, the body's TLRs recognize them and stimulate an immune response. Thus, in addition to symptoms caused by the microbial infection itself, sepsis is also characterized by symptoms of acute inflammation brought on by the host's immune response. These latter symptoms may include fever and elevated white blood cell count, or low white blood cell count and low body temperature. SIRS is characterized by hemodynamic compromise and resultant metabolic dysregulation, and may be accompanied by symptoms such as high heart rate, high respiratory rate and elevated body temperature. The immunological response also causes widespread activation of acute phase proteins, affecting the complement system and the coagulation pathways, which then cause damage to the vasculature and organs. Various neuroendocrine counter-regulatory systems are then activated as well, often compounding the problem.
Sepsis is often treated in the intensive care unit with intravenous fluids and antibiotics and/or antiviral compounds. However sepsis progresses quickly, and so even with immediate and aggressive treatment, severe sepsis can lead to organ failure and death. Severe sepsis is estimated to cause 215,000 deaths per year in the United States, more than acute myocardial infarction, stroke or pneumonia, which is likely due to late diagnosis or misdiagnosis of sepsis.
Thus, there is a need for early molecular markers in detecting sepsis.